1. Field of the Invention
The present invention relates to light guide plates used in products such as liquid crystal displays.
2. General Background
A typical LCD device comprises an LCD panel, and a backlight system mounted under the LCD panel for supplying light beams thereto. There are two types of backlight systems: the edge type and the direct type. The edge type backlight system mainly comprises a light guide plate, and a light source disposed adjacent to a thin side of the light guide plate. The light guide plate is used for guiding the light beams emitted by the light source, in order to uniformly illuminate the LCD panel. In contrast, the direct type backlight system employs light sources placed in an air-filled cavity under the LCD panel, and a diffuser disposed between the LCD panel and the light sources.
Referring to FIG. 6, a light guide plate 10 comprises a light incident surface 101, a light emitting surface 102 adjacent to the incident surface 101, and a bottom surface 103 opposite to the emitting surface 102. A plurality of v-shape cuts 11 are formed at the bottom surface 103. The cuts 11 are uniform, and define triangular cross-sections. The cuts 11 are oriented parallel to the incident surface 101.
FIG. 7 is a side view of the light guide plate 10 shown in FIG. 6, showing essential light paths. Incident light beams enter the light guide plate 10 through the incident surface 101. The v-shape cuts 11 can scatter and reflect the light beams, so as to totally eliminate internal reflection of the light beams and make the light beams evenly emit from the emitting surface 102. An angle of each of the cuts 11 can configured in order to appropriately direct the light beams reaching the cuts 11. Thus a range of emission of light from the light guide plate 10 is controllable.
However, all the cuts 11 are parallel to each other. That is, the cuts 11 are arranged along a single direction. The cuts 11 cannot eliminate internal reflection of all light beams, and portions of the light beams are wasted. Therefore, the light guide plate 10 may have low brightness and low utilization of light.
What is needed, therefore, is a light guide plate having high brightness and high utilization of light.